Lubricating oil composition



3,459,000 Patented Aug. 5, 1969 3,459,660 LUBRICATING 01L COMPOSITION William T. Shepherd, Port Arthur, Tex., assignor to Texaco Inc., New York, N.Y., a corporation of Delaware N Drawing. Filed Oct. 14, 1966, Ser. No. 586,637 Int. Cl. Cm 1/44 US. Cl. 25237.2 8 Claims ABSTRACT OF THE DISCLOSURE Mineral lubricating oil composition containing a hydrocarbyl phosphite, an aliphatic hydrocarbon-substituted organic tin salt and a trialkylated phenol.

This invention relates to an improved lubricating oil composition for use in refrigeration systems. The lubricating oil composition of the invention is characterized by having greatly improved stability and compatibility in the unique environment of a mechanical refrigeration system wherein the lubricant is in intimate contact with a halo-alkane refrigerant.

Refrigeration systems, such as mechanical compressor refrigerators and air conditioning units, operate by effecting the compression and expansion of a refrigerant. A gaseous refrigerant is compressed and cooled in one stage of the system where the contained heat is removed and is then passed through an expansion valve where the pressure is reduced and the liquid evaporates to absorb heat in the expansion stage of the system. Alternate cycles of compression and expansion are continuously carried out while the refrigeration system is in operation. Refrigeration systems of the type described are enclosed or hermetically sealed and must contain a lubricant Within the sealed system which is effective to lubricate the moving parts thereof.

The base oils used in lubricants for refrigeration systems must have certain essential characteristics. These oils must have a low pour point s0 that they will flow freely at extremely low temperatures. The base oil must also have low Haze and Floc points, that is low tempera tures at which any haziness or fioc formation takes place in a mixture of the lubricant and refrigerant, in order to avoid clogging of the fine orifices in the system. Refined mineral oils and certain sulfonic oils are useful for formulating lubricants for refrigeration systems because of their excellent oiliness characteristics and other low temperature characteristics.

conventionally refined base oil stocks per se are generally not used in refrigeration systems. This is because of the unusual conditions existing in such systems whereby the lubricant and refrigerant are in intimate contact or are admixed with one another. Under the conditions of elevated temperature and pressure which occur in a refrigeration system, the base oil and halo-alkane refrigerant react with one another. This reaction is believed to bring about the formation of halogen-acid reaction products which are corrosive and lead to degradation of and sludging in the lubricant in the system.

A major essential requirement for lubricants for refrigeration systems is that they be stable and compatible with halo-alkane refrigerants over long periods of time. This is normally accomplished by severe refining of the base oil and/or by incorporating suitable additives in a conventionally refined refrigeration oil. It has now been discovered that a novel combination of additives in the base oil cooperate to provide an outstanding level of stability and compatibility in the lubricant of the invention.

In accordance with the present invention, it has been discovered that a combination of additives comprising a hydrocarbyl phosphite, a hydrocarbyl tin ester compound and an alkyl-substituted phenol when incorporated in a suitable base oil provides a compounded lubricant for refrigeration systems that is characterized by being remarkably stable against deterioration and sludge 'forma tion.

More specifically, the lubricating oil composition of the invention comprises a major proportion of a mineral lubricating oil, having an SUS at 100 F. in the range from about to 600, a pour point below about 20 F., a Haze point below 30 F. a Floc point below 50 F. containing from about 0.005 to 1.0 percent by weight of a hydrocarbyl phosphite compound corre sponding to the formula:

in which R is a hydrocarbyl radical having from 1 to 18 carbon atoms, X is an oxygen or sulfur atom, in is an integer from 2 to 3, n is an integer from 0 to 1 and the sum of in plus it equals 3, from about 0.001 to 0.5 percent by weight of a tin compound corresponding to the formula:

R2Sn(0( /R)2 in which R is an aliphatic hydrocarbon radical having from 1 to 8 carbon atoms and R" is an aliphatic hydrocarbon radical having from 8 to 18 carbon atoms, and from about 0.005 to 1.0 weight percent of a substituted alkylphenol corresponding to the formula:

in which R is an aliphatic hydrocarbon radical having from 1 to 10 carbon atoms.

The base oil used for formulating the lubricant of the invention is a wax-free, low aniline point mineral oil, preferably naphthene oil although paraflin oils are suitable.

of the invention is one having the Pour, Haze and Floc points of the above typical base oil.

In systems using refrigerants which are miscible with the oil, fioc point and haze point tests are valuable indicators of the low temperature performance of the oil. Both of these tests are conducted on a mixture of ten percent oil in Refrigerant 12 (Freon l2) sealed in a glass tube and cooled at a rate of 12 F. per minute with observations after each 5 F. drop in temperature. The temperature at which the first evidence of haziness is discernible in the oil is the Freon 12 Haze point or haze point. On further cooling, the wax particles coalesce and individual agglomerates may be observed. The temperature at which the initial agglomerates or flocs are observed is the Freon 12 F point or floc point. The Floc point test is disclosed on page 126 of vol. 53, No. 10, 1967 issue of Texaco Inc.s publication Lubrication.

The hydrocarbyl phosphite component of the refrigeration oil of the invention corresponds to the formula:

in which R is a hydrocarbyl radical having from 1 to 18 carbon atoms, X is an oxygen or sulfur atom, in is an integer from 2 to 3, n is an integer from to 1 and the sum of m plus n equals 3. The preferred compounds are those in which R is an alkyl radical having from 8 to 18 carbon atoms and X is an oxygen atom. Effective phosphites include trimethyl phosphite, triethyl phosphite, tri- (Z-ethylhexyl) phosphite, tridecyl phosphite, trilauryl phosphite, tristearyl phosphite, triphenyl phosphite, diethyl phosphite, dibutyl phosphite, dilauryl phosphite, dioleyl phosphite, distearyl phosphite, trilauryl trithiophosphite, dilauryl trithiophosphite, tridecyl trithiophosphite, tri-(Z-ethylhexyl) trithiophosphite, diphenyl phosphite, and phenyldistearyl phosphite. The preferred concentration of the phosphite compound is from about 0.01 to 0.1 weight percent.

The effective tin compounds in the lubricant of the invention correspond to the formula:

II memo cam in which R is an aliphatic hydrocarbon radical having from 1 to 8 carbon atoms and R" is an aliphatic hydrocarbon radical having from 8 to 18 carbon atoms. The preferred tin compounds are those in which the alkyl radicals represented by R have from 4 to 6 carbon atoms and those represented by R" have from 12 to 14 carbon atoms. Examples of effective tin compounds that can be employed in the refrigerating oil of the invention include dibutyl-tin-dilaurate, dipropyl tin diluarate, diamyl tin dilaurate, dibutyl tin dimyristate, dipropyl tin dimyn'state, dihexyl tin dilaurate, diamyl tin distearate, diethyl tin didodecanoate and the like. The preferred concentration of said tin compound is from about 0.01 to 0.1 Weight percent.

The alkylphenols employed in the lubricating oil composition correspond to the formula:

in which R' is an aliphatic hydrocarbon having from 1 to carbon atoms. The preferred alkylphenols are the ortho-alkylphenols in which the total number of carbon atoms in the alkyl substituents is from about 6 to 15. Examples of effective alkylphenols are 4-methyl-2,6-di-t-butylphenol, 4-ethyl-2,6-di t butylphenol, 4-butyl-2, 6-di-tbutylphenol, 4-methyl-2,6-diarnylphenol, 4-methyl-2,6-dihexylphenol and the like. The preferred concentration of the alkylphenol is in the range from 0.01 to 0.2.

The combination of three additives, namely a hydrocarbyl phosphite, tin compound and alkylphenol, in a suitable base oil is critical and essential to prepare the refrigeration oil of this invention. If any one of the additives is omitted, the resultant lubricating oil becomes defective in one or more properties and is unsatisfactory for the purposes intended as will be evident from the examples below. The actual preparation of the lubricating oil composition from its components is a simple matter within the skill of the art. The noted amounts of the additives can be readily blended with the base oil to make up the finished formulation.

The examples in the tables below illustrate the practice of this invention. In the examples, the concentration of the additive employed is given in weight percent. The base oil employed in these examples was a highly refined, wax- '4 free oil particularly intended for use in refrigeration systems. This base oil had the following properties:

Gravity 25.2 Flash, COC F. 355 SUS at F. 153 Color, ASTM 1.0 Pour, F 55 Neut No. (ASTM D974) 0.01 Haze, F. 60 Floc 80 Dielectric strength, volts 40,000 Water, p.p.m 15

The lubricating oils of the invention were tested for stability in a copper plating proclivity test and in sealed tube tests. In the copper plating test, equal volumes of the oil undergoing test and carbon tetrachloride are added to a bottle together with a steel and copper couple. The bottle is sealed and maintained at an elevated temperature of F. The test cells are visually observed daily for signs of galvanic action or transfer of copper to the steel strip. This is evidenced by a bright copper plating on the steel strip.

In this test, non-inhibited base oils will fail in a period from 48 to 72 hours as evidenced by copper plating of the steel strip. A minium of 400 hours under the accelerated aging test conditions Without any signs of copper plating on the steel strip is an acceptable criterion for the lubricating oil to pass this test and is the actual requirement of a major air-conditioner manufacturer. The results of the copper plating tests are given in Table I below:

cone. wt. copper percent plating 1 Lubricant composition Example 1, Base oil 48, 72 Exagple 2:1

use 01 Distearyl phosphite. 0. 05 72 Example 3:

Base oil Tristearyl phosphite 0. 05 Example 4:

Base oil Trideeyl phosphite 0. 05 Example 5:

Base oil Tridecyl phosphite 4-rnethyl-2,6-di-t-butylphenol Example 6:

Base oil Dibutyl tin dilaurate 0. 03 4-methyl-2,6-di-t-butylphenol- 0. 03 Exarnp 7 Dibutyl tin dilaurate 4rnethyl-2,fi-di-t-butylphenol Distearyl phosphite Example 8:

Base oil Dibutyl tin dilaurut-e 0. 03 4-methyl-2,G-di-t-butylphen 0. 03 Dioleyl phosphite 0. 03 Example 9:

gage oil 1-l i utyl tin i aurate 0. 03 4methyl-2,6-di-tbutylphenol--. o. 03 1 2 456 Tridecyl phosphite 0. 05 Example 10:

Base oil Dibutyl tin dilaurate 0. 03 3 423 4-methyl-2,6-di-t-buWlphenoL 0. 03

Trilanryl trithiophosphite Example 11:

Base oil Dibutyl tin dilaurate 4-methyl-2,fi-di-t-butylphen Phenyl didecyl phosphite ing Refrigerator Oils by H. M. Elsey, L. C. Flowers and J. B. Kelley which appeared in Refrigerating Engineering for July 1952, pages 737742. Briefly, the procedure employed involves putting equal amounts of the lubricant being tested and Refrigerant 12 (dichlorodifiuoromethane CCI F into a Pyrex glass test tube together with copper wire and a steel strip to form a couple in the oil-refrigerant mixture. The test tube is hermetically sealed and then aged at 347 F. for 14 days.

Instability in the lubricant will bring about or permit a reaction between the lubricant and Refrigerant 12 with the result that some Refrigerant 22 (monochlorodifiuoromethane CHClF is produced in the sealed tube. The amount of Refrigerant 22 produced is determined by analysing the mixture in the test tube after the 14 days accelerated aging period. An oil passes this stability test if there has been substantially no production of Refrigerant 22 during the test period. The results of this test with the lubricants of the invention are given in Table 11 below:

TABLE II.14 DAY ELSEY TEST Additive Refrigerant cone. wt. 22, wt.

Lubricant composition percent percent Example 12, Base oil 0.77 Example 13:

Base oil Dibutyl tin dilaurate 0.03 0.22

4-methyl-2,fi-ditbutylphenol 0. 03 Example 14:

Base oil Dibutyl tin dilaurate 0.03 O 00 4-methyl-2,G-di-t-butylphenoL 0.03 i

Dioctadecyl phosphite 0. 06 Example 15:

Base oil Dibutyl tin dilaurate 0. 03

4-methyl-2,6-di-t-butylphenol 0. 03 J Dilauryl trithiophosphite 0. 06 Example 16:

ase 0 Dibutyl tin dilaurate 0.03 0 00 Tridecylphosphite 0. 03

Only the lubricants containing the three essential components exhibit stability in the presence of Refrigerant l2 and prevent reaction with and the formation of Refrigerant 22. These examples show the outstanding stability of the lubricating compositions of the invention. The lubricants of this invention are also equally or more stable in the presence of other refrigerants, such as, trichloromonofiuoromethane, tetrafluoromethane, monochlorotrifluoromethane and dichlorotetrafiuoroethane.

Obviously, many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. A lubricating oil composition effective for use in a refrigeration system containing a halo-alkane refrigerant having an SUS viscosity at 100 F. in the range from about 75 to 600, a pour point below F. and a Floc below -50 F., containing from about 0.005 to 1.0 weight percent of a hydrocarbyl phosphite compound corresponding to the formula:

in which R is a hydrocarbyl radical having from 1 to 18 carbon atoms, X is an oxygen or sulfur atom, m is an integer from 2 to 3, n is an integer from 0 to 1 and the sum of in plus it equals 3, from about 0.001 to 0.5 weight percent of a tin compound corresponding to the formula:

in which R is an aliphatic hydrocarbon radical having from 1 to 8 carbon atoms and R" is an aliphatic hydrocarbon radical having from 8 to 18 carbon atoms, and from about 0.01 to 0.2 weight percent of a substituted alkylphenol corresponding to the formula:

in which R is an aliphatic hydrocarbon radical having from 1 to 10 carbon atoms.

2. A composition according to claim 1 in which said mineral lubricating oil has a pour point below 40 F. and a Floc below F.

3. A composition according to claim 1 in which R has a value from 8 to 18, R has a value from 4 to 6 and R has a value from 12 to 14.

4. A composition according to claim 1 in which said phosphite is distearyl phosphite.

5. A composition according to claim 1 in which said phosphite is tridecylphosphite.

6. A composition according to claim 1 in which said phosphite is dioleyl phosphite.

7. A composition according to claim 1 in which said phosphite is trilauryl trithiophosphite.

8. A composition according to claim 1 in which said phosphite is diocetdecyl phosphite, and tin compound is clibutyl tin dilaurate and said phenol is 4-methyl-2,6-di-tbutylphenol.

References Cited UNITED STATES PATENTS 2,080,299 5/1937 Benning et al. 2524918 XR 2,975,137 3/1961 Stuart 252372 XR 3,056,823 10/ 1962 Hechenbleikner et al.

25249.8 XR 2,265,582 12/1941 Stevens et a1 25252 XR 3,129,185 4/ 1964 RiZZuti et a1 25268 2,186,028 1/1940 Koethen 25268 OTHER REFERENCES Lubrication, vol. 47, No. 7 (July 1961), pp. 78-84 (pub. by Texaco Inc.).

DANIEL E. WYMAN, Primary Examiner W. CANNON, Assistant Examiner US. Cl. X.R. 

